This invention relates to an apparatus and method to detect a magnetic field. The apparatus used in the method of the present invention is generally described in commonly assigned U.S. Pat. No. 4,851,762 made by the same inventors and entitled "A Novel Technique Using Magnetic Field Dependent Phase Detection for Detection of Superconductivity" and incorporated herein by reference. This patent teaches that the phase transition temperature (T.sub.c) of a superconductor may be determined using a magnetically modulated resistance measurement. Any type of resistance device may be used.
A related commonly assigned patent application is Ser. No. 07/325,823 entitled "A Method for Detection of Weak Links in the Current Path of Electrically Continuous Superconductors" filed Mar. 30, 1989, U.S. Pat. No. 4,904,929. This method also uses a magnetically modulated resistance measurement but is limited to measuring the dc or ac resistance.